This invention relates to circular saws of the type comprising a table, a pivot member on tile table and a saw assembly pivoted about a pivot axis with respect to said pivot member, whereby said saw assembly carrying a motor driven blade can be plunged into a workpiece supported on the table.
Such saws are known and described in published patent documents such as EP 0133666 and EP 0450400. These saws are useful and have numerous possibilities for enhancement to improve the capacity, capability and efficiency, not to mention cleanliness and safety of their arrangements. On the other hand, all these features add complexity and cost, and may render the saw user unfriendly.
The present invention particularly relates to saws of the type described above but which in addition have the table mounted in a frame such that the table may be inverted, as by pivoting about an axis, so that the saw assembly is then beneath the table. The table is in addition provided with a slot so that the blade call protrude through the slot to render tile saw a bench or table saw. Such saws are shown and described in DE 1628992 and EP 0502350.
Both EP 0133666 and EP 0450400 mentioned above describe saws in which the saw assembly comprises an upper guard and a lower guard for the blade. The upper guard is formed from the housing of the assembly and permanently covers a top part of the blade. A bottom part of the blade is covered by the lower guard but this must be withdrawn in use so that the blade is exposed when required to perform cutting operations.
A handle is disposed on the upper guard by means of which a user can pivot the saw assembly up and down to perform cutting operations on a workpiece supported on the table.
The lower guard may be opened entirely by an actuating lever disposed on said handle. Alternatively the guard may be opened automatically by pivoting of the saw assembly, there being provided a connection between the guard and the pivot member for this purpose. A further alternative is that the guard may be opened partly by either of these arrangements and only further opened by direct contact with a workpiece.
Although not explicitly described in EP 0450400, the saw to which that specification relates employs a parallelogram lever arrangement. The upper guard is pivoted with respect to the saw assembly. A parallelogram lever extends between the upper guard and the pivot member and lies parallel a line joining the pivot axis of the guard to the assembly and the pivot axis of the assembly to the pivot member. This arrangement serves to maintain the orientation of the upper guard with respect to the pivot member and hence to the table. Apart from a minor benefit when in the chop saw mode the primary benefit is provided when the saw is in its bench saw mode. This is because a riving knife is attached to the upper guard when the saw is in bench saw mode and it is important that the tip of the riving knife is almost level with the top of the saw blade. It needs to be above the blade where the workpiece being cut is to be entirely separated, and in which case a guard is usually mounted on the knife above the level of the blade, or just below the level of the blade when so-called pocket cuts are made, that is to say, grooves are cut in the workpiece. In any event, the orientation of the knife with respect to the blade should remain constant for all positions of the blade and it is for this reason that a parallelogram arrangement is frequently employed.
It is of course necessary in bench saw mode of the saw to provide for different positions of the blade with respect to the table, that is to say, the extent to which it protrudes through the slot in the table and hence the depth of cut of the blade. It is well known that the blade should protrude through the slot only sufficiently to leave a small amount of blade above the workpiece (assuming complete separation of the workpiece is required) so that the maximum number of teeth on the blade are in contact with the workpiece at any one time. For pocket cuts, a more precise adjustment of the depth of cut is required.